Synthesis of a missing structural link: the first trigonal planar B₄units in the novel complex boride Ti_1+xOs_2−xRuB₂(x = 0.6)

Abstract

The newly synthesized boride Ti(1+x)Os(2-x)RuB(2) (x = 0.6) has a novel structure featuring one-dimensional chains of titanium atoms, one-dimensional strings of face-sharing empty tetrahedral and square pyramidal clusters and, most importantly, trigonal planar and strongly bonded B4 units with a B-B distance of 1.89 A.

Sn-flux syntheses, characterizations and bonding analyses of OsB and TiB2

“…In agreement with this assessment the energy integral ICOHP for an Os-B contact (−3.20 eV/bond) is more than twice as large as the value obtained for the Os-Os contact (−1.09 eV/bond). The ICOHP value (−3.20 eV/bond) of the Os-B interaction is also comparable with the average values (−2.82 eV/bond) and (−3.00 eV/bond) obtained, respectively, in the ternary Ti 1.6 Os 2.4 B 2 [30] (electronic structure calculations made in this work) and in the quaternary Ti 1.6 Os 1.4 RuB 2 [31]. The very low ICOHP value (−0.05 eV/bond) obtained for the average B-B distances shows the insignificance of the B-B interaction, as could be expected for the rather long B-B distance (2.87 Å).…”

“…A trigonal planar B 4 unit, which can be the starting point for building the boron layer in TiB 2 (see Fig. 5), was found for the first time in Ti 1.6 Os 1.4 RuB 2 [31] and later confirmed in isotypic Ti 1.6 Os 2.4 B 2 [30]. between the titanium atoms.…”

Rational Synthetic Tuning between Itinerant Antiferromagnetism and Ferromagnetism in the Complex Boride Series Sc2FeRu5−nRhnB2 (0≤n≤5)

“…[4] The average M'-B distance in each structure ( % 2.20 ) is the shortest one, and it is slightly wider than the average covalent radii sum of 2.07 (2.07 for either Ru-B or Rh-B); these interactions very probably correspond to the strongest bonds. Similar RuÀB and RhÀB bonds were found in the phases Sc 2 Ru 5 B 4 (2.18 ), [8] Ti 1.6 Os 1.4 RuB 2 (2.16 ), [12] FeRh 6 B 3 (2.15 ), [13] Fe x M' 7Àx B 3 (2.14 for M': Ru and 2.13 for M': Rh), [14] and Sr 2 Ru 7 B 8 (2.05-2.20 ).…”

The complex metal-rich boride Ti1+xRh2−x+yIr3−yB3 (x=0.68, y=1.06) with a new structure type containing B4 zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

“…Indeed, rhodium is found in both layers in this structure, although a slight preference for the z¼0 layer (Ti layer) is also observed. This distribution of transition metals is also found in other boride phases containing isolated boron atoms as well as boron fragments: For example in all phases adopting the Ti 1 þ x Os 2 À x RuB 2 -type structure [12] and in the crystal structure of the recently discovered Ti 7 Rh 4 Ir 2 B 8 [15] phase, which is the first solid state phase containing the rare planar B 6 ring in its structure.…”

“…At the end of the nineties another B 4 unit, namely the B 4 tetrahedron was discovered in Ni 20 AlB 14 (M:B¼1.5) [11]. A few years ago (in 2006) a trigonal planar arrangement of four boron atoms was found in the crystal structure of Ti 1 þ x Os 2 À x RuB 2 (x¼0.6; M:B¼2) [12]. The discovery of this trigonal planar B 4 unit was very important because the boron layers observed in the structures of many intermetallic borides with high boron amount, like in MgB 2 (AlB 2 -type) [13], can be thought of as being built up by such a trigonal planar B 4 unit.…”